An image forming apparatus includes a correcting portion, an image forming device, and a fixing device that is one of a first fixing device including a first pair of rotatable members forming a first nip under a first load, and a second fixing device including a second pair of rotatable members forming a second nip under a second load that is less than the first load. A mounting portion selectively mounts one of the plurality of fixing devices. A detector detects a density of a toner image fixed on a recording material. When the fixing device is the first fixing device, an executing portion permits execution of a calibration process for generating a correction condition on the basis of a result of detection of a predetermined toner image by the detector, and, when the fixing device is the second fixing device, the executing portion prohibits execution of the calibration process.